Pivot integrated actuator assembly for a hard disk drive

ABSTRACT

Actuator arm pivot assemblies used in hard disk drives carry the read/write heads used for data transfer to/from the disk surface. Actuator arm pivot assemblies use pivot cartridges for the pivoting mechanism. Typical pivot cartridges are built on a thin sleeve made out of a stiff material, such as stainless steel. This sleeve is expensive to manufacture relative to other parts of the assembly. Eliminating the sleeve from an actuator arm pivot assembly achieves significant manufacturing cost savings.

FIELD

The invention relates to hard disk drives, and more specifically,actuator arm assemblies for hard disk drives.

BACKGROUND

Hard disk drives are used in computers and other electronic devices fornonvolatile memory. A hard disk drive allows fast random access readingand writing of data to nonvolatile memory at a reasonable cost.

A hard disk drive usually consists of one or more platters coated with amagnetic material that can be polarized in order to store bits ofinformation. A magnetic read/write head, which is attached to anactuator arm, reads and writes information to the disk surface. Toaccess different tracks on the disk surface, the actuator arm pivots tochange the radial location of the head relative to the center of thedisk. A voice coil motor is commonly used to control the movement of theactuator arm.

Actuator arm assemblies commonly use pivot cartridge assemblies to allowthe actuator arm to pivot relative to the hard drive disk. A pivotcartridge usually consists of a sleeve, usually made of stainless steel,two or more bearings, and a shaft.

FIG. 1 shows a prior art pivot cartridge 10 and actuator arm 12. Theactuator arm 12 holds the voice coil 14, which is used for controllingmovement. The actuator arm 12 may be attached to the pivot cartridge 10with an adhesive applied to an inner surface 13 of the actuator arm 12,with a mechanical fastener such as a screw 20 threaded into the actuatorarm 12 at a threaded hole 22, or with a compression ring (c-ring) 16 andspring washer 18 combination.

FIG. 2 shows a cross section of a typical prior art pivot cartridge 10.In this example the actuator arm 12 and pivot cartridge 10 are assembledwith a c-ring 16 and spring washer 18. The pivot cartridge 10 includes asleeve 30, an upper bearing 26, a lower bearing 24, and a shaft 28. Theshaft 28 has a flange 29 that separates the upper bearing 26 and lowerbearing 24. The bearings 24, 26 are usually attached to the sleeve 30with an adhesive. Typically, a preload force (500 g for example) isapplied to the pivot cartridge assembly 10 while the adhesive cures.Adhesives are used, because the relatively high preload force cannot bemaintained with other methods such as a frictional or interference fit.A suitable adhesive is an ultraviolet light curing adhesive such asLoctite 648UV.

The sleeve of a typical pivot cartridge, which may have a wall thicknessof less than 1 mm, is very expensive to manufacture. If the sleeve couldbe eliminated from the actuator arm pivot assembly, the disk drivemanufacturing cost would be significantly reduced. Thus, there is a needfor a sleeveless actuator arm pivot assembly.

SUMMARY

An actuator arm pivot assembly is described with a shaft, bearings, andan actuator arm. One embodiment comprises a pivot assembly with arotating shaft. Another embodiment comprises a pivot assembly with astationary shaft.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a prior art actuator arm pivot assembly.

FIG. 2 shows a prior art cross sectional view of a pivot cartridge.

FIG. 3 shows a first example of an actuator arm pivot assembly.

FIG. 4 shows a second example of an actuator arm pivot assembly.

FIG. 5 shows the pivot assembly of FIG. 4 with an attached actuator arm.

DESCRIPTION

The pivot cartridge sleeve commonly used in actuator arm assemblies isusually made of stainless steel and has a wall thickness of less than 1mm. The very thin wall renders the sleeve difficult to manufacture,increasing the manufacturing expense and resulting in a high part cost.Designing the assembly without a sleeve achieves significant costsavings.

FIG. 3 shows an example of a sleeveless actuator arm pivot assembly. Theshaft 40 has a flange 41 that restrains the lower bearing 44. Theactuator arm 42 is positioned between the upper bearing 46 and the lowerbearing 44. The bearings 44, 46 prevent axial movement of the arm 42.The arm 42 is shaped such that a gap 43 exists between the arm 42 andthe shaft 40. The gap 43 allows the arm 42 to freely rotate around theshaft 40 without contact between the arm 42 and the shaft 40.

The assembly shown in FIG. 3 can be assembled by first placing the lowerbearing 44 on the shaft 40. Next, the actuator arm 42 is placed on thelower bearing 44. Then the upper bearing 46 is placed on the shaft 40and in contact with the actuator arm 42. An adhesive is placed betweenthe shaft 40 and the inner race 54 of the upper bearing 46 either beforeor after the upper bearing 46 is placed on the shaft 40. A preload isapplied to the inner race 54 of the upper bearing 46 before the adhesiveis cured. The preload securely clamps the actuator arm 42 between thelower and upper bearings 44, 46. The preload also stiffens the assembly.Stiffening the assembly is desirable as it increases the dynamicresponse of the system and leads to faster track seek times. After theadhesive is cured, the preload is removed. An optional threaded hole 45in the top of the shaft 40 allows the outside cover of the disk drive orother structural part to be secured to the shaft 40. This may furtherincrease the stiffness of the pivot assembly.

The actuator arm 42 pivot assembly described above uses a stationaryshaft 40 with a rotating actuator arm 42. It is also possible to buildan actuator arm 42 pivot assembly with a rotating shaft 40.

FIG. 4 shows a second example of a sleeveless actuator arm pivotassembly without the actuator arm 42 attached. The base 58 has a hole 59that can receive lower and upper bearings 44, 46. The frame of the diskdrive or other structural member may be used as the base 58. The shaft40 is held in place by the bearings 44, 46 and is allowed to rotaterelative to the base 58. The shaft 40 has a flange 61 that keeps theshaft 40 and bearings 44, 46 from moving in the axial direction. Apreload on the outer race 52 of the upper bearing 46 is shown.

The assembly shown in FIG. 4 can be assembled by first placing the lowerbearing 44 in the hole 59. Next, the shaft 40 is placed in the bore ofthe lower bearing 44. Then the upper bearing 46 is placed in the hole 59and on the shaft 40. An adhesive is applied to the interface 60 betweenthe hole 59 and the outer race 52 of the upper bearing 46 either beforeor after the upper bearing 46 is placed on the shaft 40. A preload isapplied while the adhesive cures. After the adhesive is cured, thepreload is removed.

FIG. 5 shows the same sleeveless actuator arm 42 pivot assembly of FIG.4 with the actuator arm 42 attached to the shaft 40. The actuator arm 42can be attached with an adhesive, a mechanical fastener, or othersuitable means. FIG. 5 shows the actuator arm 42 attached with a screw62. Also shown is the disk 64 of the hard disk drive. In this example,the disk 64 overlaps both the outer race 52 of the upper bearing 46 andthe outer race 50 of the lower bearing 44. Overlapping the disk 64 withelements of the pivot assembly leads to a more compact hard disk drive.A more compact hard disk drive is desirable as it requires less space inthe end product and allows greater design flexibility.

The embodiments of FIGS. 3 and 5 discussed above can have manyvariations. For example, it might be desirable to use lower and upperbearings 44, 46 with different outer diameters. Likewise, it might bedesirable to use lower and upper bearings 44, 46 with different innerbores. The shaft 40 may have a plurality of flanges or equivalentfeatures to axially place the shaft 40, bearings 44, 46, and/or actuatorarm 42. The shaft 40 may also have one or more flanges designed tostabilize the actuator arm 42 against the shaft 40. In addition, thehole 59 in the base 58 shown in FIGS. 4 and 5 may have multiple boresizes to accommodate different bearing diameters.

It should also be apparent that sleeveless pivot assemblies can beconstructed with multiple actuator arms for disk drives with multipleplatters. Such an assembly might require more than two bearings and morecomplex profiles for the shaft 40 and/or the hole 59 in the base 58.

It will be apparent to one skilled in the art that the describedembodiments may be altered in many ways without departing from thespirit and scope of the invention. Accordingly, the scope of theinvention should be determined by the following claims and theirequivalents.

1. A system comprising: a shaft; an upper bearing disposed on the shaft;a lower bearing disposed on the shaft; and at least one actuator armdisposed on the shaft, where the system does not include a sleeve forreceiving the bearings.
 2. The system of claim 1, wherein the upperbearing and the lower bearing have equivalent inner bores.
 3. The systemof claim 1, wherein the upper bearing and the lower bearing havedifferent inner bores.
 4. The system of claim 1, wherein the upperbearing and the lower bearing have equivalent outer diameters.
 5. Thesystem of claim 1, wherein the upper bearing and the lower bearing havedifferent outer diameters.
 6. The system of claim 1, wherein the upperbearing overlaps a disk of a hard disk drive.
 7. The system of claim 1,wherein the lower bearing overlaps a disk of a hard disk drive.
 8. Anactuator arm system for a hard disk drive, the system comprising: ashaft; a lower bearing disposed on the shaft; an upper bearing disposedon the shaft; and an actuator arm disposed between the upper bearing andthe lower bearing, where the upper bearing and the lower bearing preventthe actuator arm from moving along an axis of the shaft.
 9. The systemof claim 8, wherein the system does not include a sleeve to receive thebearings.
 10. The system of claim 8, wherein the shaft includes aflange, the flange separating the lower bearing from the upper bearing.11. The system of claim 8, wherein the actuator arm is shaped such thata gap exists between the actuator arm and the shaft.
 12. The system ofclaim 8, wherein the upper bearing includes an inner race, the innerrace being attached to the shaft with an adhesive.
 13. A method ofassembling an actuator arm system for a hard disk drive comprising:placing the lower bearing on the shaft; placing the actuator arm on thelower bearing; placing the upper bearing on the shaft; applying anadhesive between an inner race of the upper bearing and the shaft;applying an axial preload force to the inner race of the upper bearing;curing the adhesive; and releasing the preload force.
 14. An actuatorarm system for a hard disk drive, the system comprising: a base, thebase having a hole; a lower bearing disposed in the hole; an upperbearing disposed in the hole; a shaft disposed in the lower bearing andin the upper bearing; and an actuator arm disposed on the shaft.
 15. Thesystem of claim 14, wherein the base comprises a frame of the hard diskdrive.
 16. The system of claim 14, wherein the shaft includes a flange,the flange separating the lower bearing from the upper bearing..
 17. Thesystem of claim 14, wherein the actuator arm is attached to the shaftwith a mechanical fastener.
 18. The system of claim 14, wherein theactuator arm is attached to the shaft with an adhesive.
 19. The systemof claim 14, wherein the upper bearing includes an outer race, the outerrace being attached to the hole with an adhesive.
 20. A method ofassembling an actuator arm system for a hard disk drive comprising:placing the lower bearing in the hole; placing the shaft in the lowerbearing; placing the upper bearing in the hole and on the shaft;applying an adhesive between an outer race of the upper bearing and thehole; applying an axial preload force to the outer race of the upperbearing; curing the adhesive; releasing the preload force; and attachingthe actuator arm to the shaft.
 21. A hard disk drive comprising: aframe; a disk for storing binary data; and a read-write head actuatorarm pivot assembly, where at least one bearing of the pivot assemblyoverlaps the disk.